Hello,
I'm using the RTC Alarm to wakeup the MCU every 10min and after 10PM, sleep for 10 hrs. However, I noticed that the RTC just actually sleeps for 8:25 min and when it wakes up, the RTC time says 10minutes have passed. To illustrate:
Current time is 12:00:00
Alarm set to 12:10:00... Enter standby mode.
.
.
<sleeps for 8 minutes and 25 seconds, checked using smartphone stopwatch>
.
.
Wake up and prints current time at 12:10 but in reality it's only 12:08:25. The RTC time is now off by 8:25 minutes like I said, and this will accumulate as I continue this loop.
I'm using the HAL_Library and LSI at 40 KHz for the RTC clock. Is this a limitation of the hardware? 15% drift is significant. If not, anything that I might have missed in the configuration?
I referred to the STM32F0 HAL examples and I'm not sure what I might have missed in the coding part.
/* Init */
void librtc_Init(void)
{
/**Initialize RTC Only
*/
hrtc.Instance = RTC;
hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
hrtc.Init.AsynchPrediv = 127;
hrtc.Init.SynchPrediv = 255;
hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
if (HAL_RTC_Init(&hrtc) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
}
/*
* Date Config
*/
void librtc_DateConfig(void)
{
RTC_DateTypeDef sdatestructure;
/*##-1- Configure the Date #################################################*/
/* Set Date: Tuesday February 18th 2014 */
sdatestructure.Year = 0x14;
sdatestructure.Month = RTC_MONTH_FEBRUARY;
sdatestructure.Date = 0x18;
sdatestructure.WeekDay = RTC_WEEKDAY_TUESDAY;
if(HAL_RTC_SetDate(&hrtc,&sdatestructure,RTC_FORMAT_BIN) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
}
/*
* Time Config
*/
void librtc_TimeConfig(TimeStampFormat* Time)
{
RTC_TimeTypeDef stimestructure;
/*##-2- Configure the Time #################################################*/
/* Set Time: 02:20:00 */
stimestructure.Hours = Time->hours;
stimestructure.Minutes = Time->minutes;
stimestructure.Seconds = Time->seconds;
stimestructure.TimeFormat = RTC_HOURFORMAT_24;
stimestructure.DayLightSaving = RTC_DAYLIGHTSAVING_NONE ;
stimestructure.StoreOperation = RTC_STOREOPERATION_RESET;
if(HAL_RTC_SetTime(&hrtc,&stimestructure,RTC_FORMAT_BIN) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
}
